Photooxidation of 4-chlorophenol sensitized by lutetium tetraphenoxy phthalocyanine anchored on electrospun polystyrene polymer fiber
- Zugle, Ruphino, Antunes, Edith M, Khene, Samson M, Nyokong, Tebello
- Authors: Zugle, Ruphino , Antunes, Edith M , Khene, Samson M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245787 , vital:51405 , xlink:href="https://doi.org/10.1016/j.poly.2011.11.005"
- Description: An electrospun polystyrene (PS) fiber incorporating tetraphenoxy phthalocyanine complex of lutetium (LuTPPc/PS) as a photosensitizer was applied for the degradation of 4-chlorophenol in aqueous solution in the presence of visible light. The photocatalytic activity of the LuTPPc in the fiber was compared to that of zinc phthalocyanine (ZnPc) incorporated into the PS fiber, and the former showed higher activity. UV–Vis spectral changes of sample solutions indicated transformation of the analyte with first order kinetics and half-lives that are within one and half hours for LuTPPc/PS. Products identified from the spectral changes and gas chromatography were benzoquinone, hydroquinone and 4,4′-dihydroxydiphenol suggesting that the photodegradation of 4-chlorophenol was through both Types I and II mechanisms.
- Full Text:
- Date Issued: 2012
- Authors: Zugle, Ruphino , Antunes, Edith M , Khene, Samson M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245787 , vital:51405 , xlink:href="https://doi.org/10.1016/j.poly.2011.11.005"
- Description: An electrospun polystyrene (PS) fiber incorporating tetraphenoxy phthalocyanine complex of lutetium (LuTPPc/PS) as a photosensitizer was applied for the degradation of 4-chlorophenol in aqueous solution in the presence of visible light. The photocatalytic activity of the LuTPPc in the fiber was compared to that of zinc phthalocyanine (ZnPc) incorporated into the PS fiber, and the former showed higher activity. UV–Vis spectral changes of sample solutions indicated transformation of the analyte with first order kinetics and half-lives that are within one and half hours for LuTPPc/PS. Products identified from the spectral changes and gas chromatography were benzoquinone, hydroquinone and 4,4′-dihydroxydiphenol suggesting that the photodegradation of 4-chlorophenol was through both Types I and II mechanisms.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical properties of novel phthalocyanines bearing non-peripherally substituted mercaptoquinoline moiety
- Yaşa, Göknur, Erdoğmuş, Ali, Uğur, Ahmet Lütf, Şener, M Kasım, Avcıata, Ulvi, Nyokong, Tebello
- Authors: Yaşa, Göknur , Erdoğmuş, Ali , Uğur, Ahmet Lütf , Şener, M Kasım , Avcıata, Ulvi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244360 , vital:51250 , xlink:href="https://doi.org/10.1142/S1088424612500940"
- Description: The synthesis, photophysical and photochemical properties of nonperipherally (a) mercaptoquinoline substituted Zn(II), TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1 H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.
- Full Text:
- Date Issued: 2012
- Authors: Yaşa, Göknur , Erdoğmuş, Ali , Uğur, Ahmet Lütf , Şener, M Kasım , Avcıata, Ulvi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244360 , vital:51250 , xlink:href="https://doi.org/10.1142/S1088424612500940"
- Description: The synthesis, photophysical and photochemical properties of nonperipherally (a) mercaptoquinoline substituted Zn(II), TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1 H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical studies of sulfur containing phthalocyanine derivatives in the presence of folic acid
- Nombona, Nolwazi, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
Photophysics and photochemistry of octaglucosylated zinc phthalocyanine derivatives
- Iqbal, Zafar, Ogunsipe, Abimbola, Nyokong, Tebello, Lyubimtsev, Alexey, Hanack, Michael, Ziegler, Thomas
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
Physico-chemical properties of lutetium phthalocyanine complexes in solution and in solid polystyrene polymer fibers and their application in photoconversion of 4-nitrophenol
- Zugle, Ruphino, Nyokong, Tebello
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243520 , vital:51160 , xlink:href="https://doi.org/10.1016/j.molcata.2012.02.010"
- Description: The photophysical and photochemical behavior of two phthalocyanine complexes of lutetium peripherally substituted with tetraphenoxy and tetra-2-pyridiloxy groups were studied in solution and when dispersed in polystyrene polymer fiber. The phthalocyanines were found not to fluoresce significantly in solution and not at all within the fiber matrix as compared with standard unsubstituted zinc phthalocyanine. They showed very promising photoactivity in solution with high singlet oxygen quantum yields. Their photoactivity within the polymer fiber matrix was also demonstrated with the photoconversion of 4-nitrophenol, a water pollutant. The photodegradation process with both phthalocyanines follows first order kinetics similar to that observed for the zinc phthalocyanine and the photo-products were found to be hydroquinone, benzoquinone and 4-nitrocatechol.
- Full Text:
- Date Issued: 2012
- Authors: Zugle, Ruphino , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243520 , vital:51160 , xlink:href="https://doi.org/10.1016/j.molcata.2012.02.010"
- Description: The photophysical and photochemical behavior of two phthalocyanine complexes of lutetium peripherally substituted with tetraphenoxy and tetra-2-pyridiloxy groups were studied in solution and when dispersed in polystyrene polymer fiber. The phthalocyanines were found not to fluoresce significantly in solution and not at all within the fiber matrix as compared with standard unsubstituted zinc phthalocyanine. They showed very promising photoactivity in solution with high singlet oxygen quantum yields. Their photoactivity within the polymer fiber matrix was also demonstrated with the photoconversion of 4-nitrophenol, a water pollutant. The photodegradation process with both phthalocyanines follows first order kinetics similar to that observed for the zinc phthalocyanine and the photo-products were found to be hydroquinone, benzoquinone and 4-nitrocatechol.
- Full Text:
- Date Issued: 2012
Prediction of water temperature metrics using spatial modelling in the Eastern and Western Cape, South Africa
- Rivers-Moore, N A, Mantel, S, Dallas, H F
- Authors: Rivers-Moore, N A , Mantel, S , Dallas, H F
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:7071 , http://hdl.handle.net/10962/d1003947 , http://www.scielo.org.za/scielo.php?pid=S1816-79502012000200002&script=sci_arttext
- Description: Key aspects of a river's temperature regime are described by magnitudes, timing and durations of thermal events, and frequencies of extreme exceedance events. To understand alterations to thermal regimes, it is necessary to describe thermal time series based on these statistics. Classification of sites based on their thermal metrics, and understanding of spatial patterns of these thermal statistics, provides a powerful approach for comparing study sites against reference sites. Water temperature regime dynamics should be viewed regionally, where regional divisions have an inherent underpinning by an understanding of natural thermal variability. The aim of this research was to link key water temperature metrics to readily-mapped environmental surrogates, and to produce spatial images of temperature metrics: 37 temperature metrics were derived for 12 months of sub-daily water temperatures at 90 sites in the Eastern Cape and Western Cape provinces, South Africa. These metrics were correlated with 16 environmental variables. Correlations enabled development of multiple regression models which facilitated mapping of temperature metrics over the study area. This approach has the potential to be applied at a national scale as more thermal time series are collected nationally. It is argued that the appropriateness of management decisions in rivers can be improved by including guidelines for thermal metrics at a regional scale. Such maps could facilitate incorporation of a temperature component into management guidelines for water resources.
- Full Text:
- Date Issued: 2012
- Authors: Rivers-Moore, N A , Mantel, S , Dallas, H F
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:7071 , http://hdl.handle.net/10962/d1003947 , http://www.scielo.org.za/scielo.php?pid=S1816-79502012000200002&script=sci_arttext
- Description: Key aspects of a river's temperature regime are described by magnitudes, timing and durations of thermal events, and frequencies of extreme exceedance events. To understand alterations to thermal regimes, it is necessary to describe thermal time series based on these statistics. Classification of sites based on their thermal metrics, and understanding of spatial patterns of these thermal statistics, provides a powerful approach for comparing study sites against reference sites. Water temperature regime dynamics should be viewed regionally, where regional divisions have an inherent underpinning by an understanding of natural thermal variability. The aim of this research was to link key water temperature metrics to readily-mapped environmental surrogates, and to produce spatial images of temperature metrics: 37 temperature metrics were derived for 12 months of sub-daily water temperatures at 90 sites in the Eastern Cape and Western Cape provinces, South Africa. These metrics were correlated with 16 environmental variables. Correlations enabled development of multiple regression models which facilitated mapping of temperature metrics over the study area. This approach has the potential to be applied at a national scale as more thermal time series are collected nationally. It is argued that the appropriateness of management decisions in rivers can be improved by including guidelines for thermal metrics at a regional scale. Such maps could facilitate incorporation of a temperature component into management guidelines for water resources.
- Full Text:
- Date Issued: 2012
Quality of life in Grahamstown, East London and Mdantsane: preliminary result
- Helliker, Kirk D, Bekker, Simon, Lambie, Eileen
- Authors: Helliker, Kirk D , Bekker, Simon , Lambie, Eileen
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144756 , vital:38376 , DOI: 10.1080/02580144.1981.10428933
- Description: A quality of life survey amongst residents of three Eastern Cape towns, viz. Grahamstown, East London, and Mdantsane, shows that the attitudes to home and neighbourhood which urban residents in the Eastern Cape develop, are fashioned in large part by both the residential “group area” in which these urban dwellers live, and by their socio-economic status. White residents, overwhelmingly, are satisfied with their diets, their municipality, their homes. They feel safe in their homes and are satisfied that police protection is available if needed. For black residents fear of poverty and unemployment, of physical violence, and dissatisfaction with an inadequate diet is widespread. Indian and coloured urban residents who are generally perceived as minorities in Grahamstown and East London, occupy an intermediate position. Their residential areas are sited close to predominantly low income black residential areas. Higher income Indian and coloured households show lower rates of dissatisfaction with diet, housing, and municipal services than the black community.
- Full Text:
- Date Issued: 2012
- Authors: Helliker, Kirk D , Bekker, Simon , Lambie, Eileen
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144756 , vital:38376 , DOI: 10.1080/02580144.1981.10428933
- Description: A quality of life survey amongst residents of three Eastern Cape towns, viz. Grahamstown, East London, and Mdantsane, shows that the attitudes to home and neighbourhood which urban residents in the Eastern Cape develop, are fashioned in large part by both the residential “group area” in which these urban dwellers live, and by their socio-economic status. White residents, overwhelmingly, are satisfied with their diets, their municipality, their homes. They feel safe in their homes and are satisfied that police protection is available if needed. For black residents fear of poverty and unemployment, of physical violence, and dissatisfaction with an inadequate diet is widespread. Indian and coloured urban residents who are generally perceived as minorities in Grahamstown and East London, occupy an intermediate position. Their residential areas are sited close to predominantly low income black residential areas. Higher income Indian and coloured households show lower rates of dissatisfaction with diet, housing, and municipal services than the black community.
- Full Text:
- Date Issued: 2012
Quinones and halogenated monoterpenes of algal origin show anti-proliferative effects against breast cancer cells in vitro:
- de la Mare, Jo-Anne, Lawson, Jessica C, Chiwakata, Maynard T, Beukes, Denzil R, Blatch, Gregory L, Edkins, Adrienne L
- Authors: de la Mare, Jo-Anne , Lawson, Jessica C , Chiwakata, Maynard T , Beukes, Denzil R , Blatch, Gregory L , Edkins, Adrienne L
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165165 , vital:41214 , DOI: 10.1007/s10637-011-9788-0
- Description: Red and brown algae have been shown to produce a variety of compounds with chemotherapeutic potential. A recent report described the isolation of a range of novel polyhalogenated monoterpene compounds from the red algae Plocamium corallorhiza and Plocamium cornutum collected off the coast of South Africa, together with the previously described tetraprenylquinone, sargaquinoic acid (SQA), from the brown algae Sargassum heterophyllum. In our study, the algal compounds were screened for anti-proliferative activity against metastatic MDA-MB-231 breast cancer cells revealing that a number of compounds displayed anti-cancer activity with IC50 values in the micromolar range. A subset of the compounds was tested for differential toxicity in the MCF-7/MCF12A system and five of these, including sargaquinoic acid, were found to be at least three times more toxic to the breast cancer than the non-malignant cell line.
- Full Text:
- Date Issued: 2012
- Authors: de la Mare, Jo-Anne , Lawson, Jessica C , Chiwakata, Maynard T , Beukes, Denzil R , Blatch, Gregory L , Edkins, Adrienne L
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165165 , vital:41214 , DOI: 10.1007/s10637-011-9788-0
- Description: Red and brown algae have been shown to produce a variety of compounds with chemotherapeutic potential. A recent report described the isolation of a range of novel polyhalogenated monoterpene compounds from the red algae Plocamium corallorhiza and Plocamium cornutum collected off the coast of South Africa, together with the previously described tetraprenylquinone, sargaquinoic acid (SQA), from the brown algae Sargassum heterophyllum. In our study, the algal compounds were screened for anti-proliferative activity against metastatic MDA-MB-231 breast cancer cells revealing that a number of compounds displayed anti-cancer activity with IC50 values in the micromolar range. A subset of the compounds was tested for differential toxicity in the MCF-7/MCF12A system and five of these, including sargaquinoic acid, were found to be at least three times more toxic to the breast cancer than the non-malignant cell line.
- Full Text:
- Date Issued: 2012
Radical thinking in South Africa’s age of retreat
- Helliker, Kirk D, Vale, Peter C J
- Authors: Helliker, Kirk D , Vale, Peter C J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71214 , vital:29818 , https://doi.org/10.1177/0021909612442654
- Description: This article traces the rise and fall of radical praxis in South Africa and offers a critique of the prevailing practices of former Marxists under post-apartheid conditions. Western Marxism emerged in the 1970s in South Africa and Marxist activists became deeply involved in the liberation movements. With the unravelling of apartheid, the main liberation forces made a social pact with capitalist forces and former Marxists embraced a statist project. In the context of the rise of ‘new’ social movements, radical thinking of a more Libertarian kind is emerging in contemporary South Africa.
- Full Text: false
- Date Issued: 2012
- Authors: Helliker, Kirk D , Vale, Peter C J
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71214 , vital:29818 , https://doi.org/10.1177/0021909612442654
- Description: This article traces the rise and fall of radical praxis in South Africa and offers a critique of the prevailing practices of former Marxists under post-apartheid conditions. Western Marxism emerged in the 1970s in South Africa and Marxist activists became deeply involved in the liberation movements. With the unravelling of apartheid, the main liberation forces made a social pact with capitalist forces and former Marxists embraced a statist project. In the context of the rise of ‘new’ social movements, radical thinking of a more Libertarian kind is emerging in contemporary South Africa.
- Full Text: false
- Date Issued: 2012
Remembering Jakes - Chancellor, our chancellor
- Authors: Badat, Saleem
- Date: 2012
- Language: English
- Type: text
- Identifier: vital:7584 , http://hdl.handle.net/10962/d1006574
- Description: From introduction: Gerwel was an exceptional, courageous, gifted and pioneering South African intellectual, scholar, leader and citizen. He had a profound commitment to creating a just and humane society. Through a long and distinguished association with the higher education sector, as an academic, dean, vice-chancellor, chairperson of the Committee of University Principals in the early 1990s, chancellor, and chairperson of the Mandela Rhodes Foundation, Gerwel was an outstanding champion of higher education. As chancellor, he challenged Rhodes to become socially conscious and think critically and imaginatively about access, equity and transformation, and about its role in socioeconomic development issues in South Africa, especially in the Eastern Cape.
- Full Text:
- Date Issued: 2012
- Authors: Badat, Saleem
- Date: 2012
- Language: English
- Type: text
- Identifier: vital:7584 , http://hdl.handle.net/10962/d1006574
- Description: From introduction: Gerwel was an exceptional, courageous, gifted and pioneering South African intellectual, scholar, leader and citizen. He had a profound commitment to creating a just and humane society. Through a long and distinguished association with the higher education sector, as an academic, dean, vice-chancellor, chairperson of the Committee of University Principals in the early 1990s, chancellor, and chairperson of the Mandela Rhodes Foundation, Gerwel was an outstanding champion of higher education. As chancellor, he challenged Rhodes to become socially conscious and think critically and imaginatively about access, equity and transformation, and about its role in socioeconomic development issues in South Africa, especially in the Eastern Cape.
- Full Text:
- Date Issued: 2012
Reverse saturation absorption spectra and optical limiting properties of chlorinated tetrasubstituted phthalocyanines containing different metals
- Tuhl, Ahmad, Manaa, Hacene, Makhseed, Saad, Al-Awadi, Nouria, Matthew, Jacob, Ibrahim, Hamada Mohamed, Nyokong, Tebello, Behbehani, Haider
- Authors: Tuhl, Ahmad , Manaa, Hacene , Makhseed, Saad , Al-Awadi, Nouria , Matthew, Jacob , Ibrahim, Hamada Mohamed , Nyokong, Tebello , Behbehani, Haider
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243498 , vital:51158 , xlink:href="https://doi.org/10.1016/j.optmat.2012.05.018"
- Description: A highly non-aggregated series of peripherally tetra(2,6-diisopropylphenoxy) substituted phthalocyanines (Pcs) containing different metals (Al, Ga, In and Zn) were prepared and their nonlinear optical properties (NLO), including the optical limiting behavior were investigated. This study explores the effect of the implanted metals along with the peripheral chlorine atoms on the NLO of the prepared complexes, thereby improving their optical limiting performance. The best wavelength at which the Pc complex exhibits the strongest nonlinear effect was determined over the low absorption window region (420–590 nm) comprised between the Q and B bands using a nanosecond pulsed laser with the aid of a Z-scan technique. The excited state absorption cross sections (σeff) have been found to be wavelength dependent with common double peaks at 505 nm and around 485 nm and the highest value was calculated for Pc1–In (1.1 × 10−16 cm2). The figure of merit spectra show different spectral structure when compared to the excited state absorption spectra and the largest figure of merit value was found to be around 107 for Pc1–In derivative. In full agreement with reverse saturation results, the optical limiting measurements, carried out at 485 nm and 532 nm for each derivative, show very low optical limiting thresholds at the former wavelength. In the continuous wave excitation regime, the Z-scan measurements, which were carried out at 632.8 and 532 nm, showed strong refractive and absorptive nonlinear effects.
- Full Text:
- Date Issued: 2012
- Authors: Tuhl, Ahmad , Manaa, Hacene , Makhseed, Saad , Al-Awadi, Nouria , Matthew, Jacob , Ibrahim, Hamada Mohamed , Nyokong, Tebello , Behbehani, Haider
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243498 , vital:51158 , xlink:href="https://doi.org/10.1016/j.optmat.2012.05.018"
- Description: A highly non-aggregated series of peripherally tetra(2,6-diisopropylphenoxy) substituted phthalocyanines (Pcs) containing different metals (Al, Ga, In and Zn) were prepared and their nonlinear optical properties (NLO), including the optical limiting behavior were investigated. This study explores the effect of the implanted metals along with the peripheral chlorine atoms on the NLO of the prepared complexes, thereby improving their optical limiting performance. The best wavelength at which the Pc complex exhibits the strongest nonlinear effect was determined over the low absorption window region (420–590 nm) comprised between the Q and B bands using a nanosecond pulsed laser with the aid of a Z-scan technique. The excited state absorption cross sections (σeff) have been found to be wavelength dependent with common double peaks at 505 nm and around 485 nm and the highest value was calculated for Pc1–In (1.1 × 10−16 cm2). The figure of merit spectra show different spectral structure when compared to the excited state absorption spectra and the largest figure of merit value was found to be around 107 for Pc1–In derivative. In full agreement with reverse saturation results, the optical limiting measurements, carried out at 485 nm and 532 nm for each derivative, show very low optical limiting thresholds at the former wavelength. In the continuous wave excitation regime, the Z-scan measurements, which were carried out at 632.8 and 532 nm, showed strong refractive and absorptive nonlinear effects.
- Full Text:
- Date Issued: 2012
Rhodes University 2012 Graduation Ceremonies Address
- Authors: Badat, Saleem
- Date: 2012
- Language: English
- Type: text
- Identifier: vital:7588 , http://hdl.handle.net/10962/d1006579
- Description: From introduction: We take pride in our striving to ensure that we are an environment in which knowledge, understanding and the intellect can flower; in being a leading postgraduate and research university that takes undergraduate studies seriously; in enjoying among the best pass and graduation rates in South Africa; in our increasing engagement with local communities; in the pursuit of equity and excellence, and in being a cosmopolitan institution with students from some 56 countries.
- Full Text:
- Date Issued: 2012
- Authors: Badat, Saleem
- Date: 2012
- Language: English
- Type: text
- Identifier: vital:7588 , http://hdl.handle.net/10962/d1006579
- Description: From introduction: We take pride in our striving to ensure that we are an environment in which knowledge, understanding and the intellect can flower; in being a leading postgraduate and research university that takes undergraduate studies seriously; in enjoying among the best pass and graduation rates in South Africa; in our increasing engagement with local communities; in the pursuit of equity and excellence, and in being a cosmopolitan institution with students from some 56 countries.
- Full Text:
- Date Issued: 2012
Rhodes University Graduation Ceremony 2012
- Authors: Rhodes University
- Date: 2012
- Language: English
- Type: text
- Identifier: vital:8135 , http://hdl.handle.net/10962/d1007245
- Description: Rhodes University Graduation Ceremonies 2012 [at] 1820 Settlers National Monument Thursday, 12 April at 18.00 [and] Friday, 13 April at 10:30; 14:30 & 18:00 [and] Saturday, 14 April at 10:30 , Rhodes University Awards, Scholarships, Bursaries and Prizes 2012
- Full Text:
- Date Issued: 2012
- Authors: Rhodes University
- Date: 2012
- Language: English
- Type: text
- Identifier: vital:8135 , http://hdl.handle.net/10962/d1007245
- Description: Rhodes University Graduation Ceremonies 2012 [at] 1820 Settlers National Monument Thursday, 12 April at 18.00 [and] Friday, 13 April at 10:30; 14:30 & 18:00 [and] Saturday, 14 April at 10:30 , Rhodes University Awards, Scholarships, Bursaries and Prizes 2012
- Full Text:
- Date Issued: 2012
Richard T. Carson: Contingent valuation: a comprehensive bibliography and history
- Authors: Snowball, Jeanette D
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71504 , vital:29859 , https://link.springer.com/content/pdf/10.1007/s10824-012-9165-7.pdf
- Description: For those of us who have been involved in willingness to pay studies for some time, Contingent Valuation: A comprehensive bibliography and history by Richard Carson is a fascinating read, tracking the early development of the method and debates around it from an insider’s perspective. As someone who has not only been involved in contingent valuation research over many years, but who has also been instrumental in shaping it, Richard Carson is the ideal author of this carefully crafted book.
- Full Text:
- Date Issued: 2012
- Authors: Snowball, Jeanette D
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71504 , vital:29859 , https://link.springer.com/content/pdf/10.1007/s10824-012-9165-7.pdf
- Description: For those of us who have been involved in willingness to pay studies for some time, Contingent Valuation: A comprehensive bibliography and history by Richard Carson is a fascinating read, tracking the early development of the method and debates around it from an insider’s perspective. As someone who has not only been involved in contingent valuation research over many years, but who has also been instrumental in shaping it, Richard Carson is the ideal author of this carefully crafted book.
- Full Text:
- Date Issued: 2012
Ritualised discourse practices of feedback in a university foundation programme: a critical investigation
- Authors: Richardson, Amy
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MA
- Identifier: http://hdl.handle.net/10962/164955 , vital:41187
- Description: In order for students to become true members of academic communities of practice they need epistemological access, including guidance on central institutional knowledge-producing processes and mastery of key academic literacy practices. A powerful source of guidance is marker feedback. Drawing on key insights from the New Literacy Studies and taking up the mandate of Critical Ethnography to improve the status quo, this thesis reports on the feedback practices in a university foundation programme. The findings are based on three micro-case studies compiled and analysed by means of methods drawn from Ethnography, Sociolinguistics and Critical Analysis in conjunction with an expanded, multimodal, APPRAISAL analysis, including adjusted categories and the author’s own feedback typologies. Two major arguments emerge: the feedback provided amounts to a set of ritualised discourse practices and its effects can be likened to the product of the children’s game of Head-body-tail. Consequently, feedback conventions are opaque and, potentially, impede epistemological access. They further entrench five sets of ideologies: (1) Students must master basic English literacy before they are coached in more complex issues such as argumentation; an assumption which leads to differential socialisation. (2) There is a single set of literacy practices that is rewarded. (3) Students have different levels of authorial authority depending on their language abilities. (4) ‘Middle students’ may benefit the most from feedback. (5) Specific comments are preferred over general ones. Analysis of feedback, furthermore, shows that markers’ frames of reference shape their pedagogy and that draft and final versions of work may be framed differently by markers. These findings require a response and, in order to facilitate epistemological access, suggestions are made for improved marker training based on the problematisation of the ritual involved in marking students’ work in this university foundation programme. , Thesis (MA)--Rhodes University, Faculty of Humanities, Linguistics, 2012
- Full Text:
- Date Issued: 2012
- Authors: Richardson, Amy
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MA
- Identifier: http://hdl.handle.net/10962/164955 , vital:41187
- Description: In order for students to become true members of academic communities of practice they need epistemological access, including guidance on central institutional knowledge-producing processes and mastery of key academic literacy practices. A powerful source of guidance is marker feedback. Drawing on key insights from the New Literacy Studies and taking up the mandate of Critical Ethnography to improve the status quo, this thesis reports on the feedback practices in a university foundation programme. The findings are based on three micro-case studies compiled and analysed by means of methods drawn from Ethnography, Sociolinguistics and Critical Analysis in conjunction with an expanded, multimodal, APPRAISAL analysis, including adjusted categories and the author’s own feedback typologies. Two major arguments emerge: the feedback provided amounts to a set of ritualised discourse practices and its effects can be likened to the product of the children’s game of Head-body-tail. Consequently, feedback conventions are opaque and, potentially, impede epistemological access. They further entrench five sets of ideologies: (1) Students must master basic English literacy before they are coached in more complex issues such as argumentation; an assumption which leads to differential socialisation. (2) There is a single set of literacy practices that is rewarded. (3) Students have different levels of authorial authority depending on their language abilities. (4) ‘Middle students’ may benefit the most from feedback. (5) Specific comments are preferred over general ones. Analysis of feedback, furthermore, shows that markers’ frames of reference shape their pedagogy and that draft and final versions of work may be framed differently by markers. These findings require a response and, in order to facilitate epistemological access, suggestions are made for improved marker training based on the problematisation of the ritual involved in marking students’ work in this university foundation programme. , Thesis (MA)--Rhodes University, Faculty of Humanities, Linguistics, 2012
- Full Text:
- Date Issued: 2012
Schottky barrier diode parameters of Ag/MgPc/p-Si structure
- Canlıca, Mevlüde, Coskun, Mustafa, Altındal, Ahmet, Nyokong, Tebello
- Authors: Canlıca, Mevlüde , Coskun, Mustafa , Altındal, Ahmet , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245820 , vital:51408 , xlink:href="https://doi.org/10.1142/S1088424612500824"
- Description: An Ag/Pc/p-Si Schottky barrier (SB) diode was fabricated. The current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements were carried out to determine the characteristic parameters such as barrier height, ideality factor and series resistance of the SB diode. The non-linear behavior of ln (I) vs. ln (V) and ln (I/V) vs. V1/2 plots indicated that the thermoionic emission theory can be applied to evaluate junction parameters for the investigated SB diode rather than space-charge limited conduction (SCLC) mechanism and bulk-limited Poole–Frenkel emission. The bulk doping concentration NB and fixed oxide charges Nf was determined from the measured high frequency C-V curve and was found to be 9.5 × 1014 cm-3 and 2.3 × 1013 cm-2, respectively. The values of barrier height obtained from Norde's function were compared with those from the forward bias current-voltage characteristic, and it was seen that there was a good agreement between barrier heights from both methods.
- Full Text:
- Date Issued: 2012
- Authors: Canlıca, Mevlüde , Coskun, Mustafa , Altındal, Ahmet , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245820 , vital:51408 , xlink:href="https://doi.org/10.1142/S1088424612500824"
- Description: An Ag/Pc/p-Si Schottky barrier (SB) diode was fabricated. The current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements were carried out to determine the characteristic parameters such as barrier height, ideality factor and series resistance of the SB diode. The non-linear behavior of ln (I) vs. ln (V) and ln (I/V) vs. V1/2 plots indicated that the thermoionic emission theory can be applied to evaluate junction parameters for the investigated SB diode rather than space-charge limited conduction (SCLC) mechanism and bulk-limited Poole–Frenkel emission. The bulk doping concentration NB and fixed oxide charges Nf was determined from the measured high frequency C-V curve and was found to be 9.5 × 1014 cm-3 and 2.3 × 1013 cm-2, respectively. The values of barrier height obtained from Norde's function were compared with those from the forward bias current-voltage characteristic, and it was seen that there was a good agreement between barrier heights from both methods.
- Full Text:
- Date Issued: 2012
Sex work: discussion document 27-29 March 2012
- Congress of South African Trade Unions (COSATU)
- Authors: Congress of South African Trade Unions (COSATU)
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: book , text
- Identifier: http://hdl.handle.net/10962/68748 , vital:29311
- Description: The aim of this paper is to resuscitate the debate on the need for decriminalization of sex work and ensure that COSATU and its affiliates further engage within structures, alliance, non -governmental organizations and with the Government in terms of the need for law reform and identify alternative policy framework. However, whatever outcome of the legal processes pertaining to sex work, should be abide by the spirit of the Constitution which is committed to advancing human rights and social justice. Sex work in South Africa is currently criminalised and is restricted by the Sexual Offences Act of 1957 (an un-amended apartheid-era law) which prohibits all activities associated with it. The criminal offences related to sex work include amongst them the keeping or participating in the management of a brothel, procuring someone to become a sex worker, soliciting or selling sex or living of the earnings of a sex worker. In 2007 through the Sexual Offences Act their clients were also criminalised In 2007, the Act was amended to criminalise buyers of sexual services too (SALRC 2009). We therefore argue that the existing laws on sex work are nothing but hypocrisy of the conservatives and elites. They do not improve the conditions of women; instead they worsen the miserable conditions that women in the sex trade already find themselves in. The missing fact is that sex work is a by-product of our patriarchal capitalist society-not something created by some “immoral prostitute” The current oppressive legislation on sex work has stimulated a lot of debates and has led to an upsurge in advocacy work by individuals and organizations around the need to either legalise or decriminalize sex work. Likewise, Cosatu as a key civil society player has also played a leading role in its endeavor to unite the working class and to defend workers from exploitation as well as finding workable solutions to the plight of the most vulnerable people in our society who find themselves with no choice but to engage in sex work. The sex industry is by nature exploitative and inherently dangerous. Women in the industry experience different degrees of abuse, coercion and violence, but all of them are harmed physically and psychologically. As a trade union movement, COSATU has an interest in the debate about sex work, from the point of view that sex work targets mainly the working class and the poor, predominantly black women. High levels of unemployment, poverty and gender inequality are key factors driving sex work. The global economic crisis has aggravated the situation for the poor majority through job losses, casualisation and ultimately increased feminization of poverty. Cosatu has already started some debates and campaigns aimed at devising ways of protecting sex workers through collective workers struggles. As such, the sex work discourse and campaign among Cosatu affiliates for decriminalization was tabled at the Federation’s 10th Congress though it was deferred because of contestation and opposition amongst delegates. However, affiliates had the responsibility to go back and make further consultations, sensitization with their structures and open up a discussion at the level of the COSATU Central Executive Committee. Indeed, it is high time that the debate on decriminalization should be concluded and that sex work be recognized as work as Arnott and Crago (2009) argue that: “The criminalisation of sex work has precluded the enforcement and protection of sex workers’ Labour rights. This disregard for sex workers as workers has left many of those employed in brothels in South Africa vulnerable to labor abuses such as withheld wages, arbitrary fines, restrictions on mobility, and confiscation of belongings including medication. Sex workers on the street or working in brothels and other agencies have no recourse if customers refuse to pay them’’1 The decriminalization of sex work should take the course of a rights- based approach which means that sex workers would be able to enjoy their basic human & labour rights and be protected against sexual harassment, violence, rape and unfair working conditions. By so doing, sex workers would be able to access non-discriminatory health care services, be more empowered and operate within the ambit of protective labour and occupational health & safety laws.
- Full Text:
- Date Issued: 2012
- Authors: Congress of South African Trade Unions (COSATU)
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: book , text
- Identifier: http://hdl.handle.net/10962/68748 , vital:29311
- Description: The aim of this paper is to resuscitate the debate on the need for decriminalization of sex work and ensure that COSATU and its affiliates further engage within structures, alliance, non -governmental organizations and with the Government in terms of the need for law reform and identify alternative policy framework. However, whatever outcome of the legal processes pertaining to sex work, should be abide by the spirit of the Constitution which is committed to advancing human rights and social justice. Sex work in South Africa is currently criminalised and is restricted by the Sexual Offences Act of 1957 (an un-amended apartheid-era law) which prohibits all activities associated with it. The criminal offences related to sex work include amongst them the keeping or participating in the management of a brothel, procuring someone to become a sex worker, soliciting or selling sex or living of the earnings of a sex worker. In 2007 through the Sexual Offences Act their clients were also criminalised In 2007, the Act was amended to criminalise buyers of sexual services too (SALRC 2009). We therefore argue that the existing laws on sex work are nothing but hypocrisy of the conservatives and elites. They do not improve the conditions of women; instead they worsen the miserable conditions that women in the sex trade already find themselves in. The missing fact is that sex work is a by-product of our patriarchal capitalist society-not something created by some “immoral prostitute” The current oppressive legislation on sex work has stimulated a lot of debates and has led to an upsurge in advocacy work by individuals and organizations around the need to either legalise or decriminalize sex work. Likewise, Cosatu as a key civil society player has also played a leading role in its endeavor to unite the working class and to defend workers from exploitation as well as finding workable solutions to the plight of the most vulnerable people in our society who find themselves with no choice but to engage in sex work. The sex industry is by nature exploitative and inherently dangerous. Women in the industry experience different degrees of abuse, coercion and violence, but all of them are harmed physically and psychologically. As a trade union movement, COSATU has an interest in the debate about sex work, from the point of view that sex work targets mainly the working class and the poor, predominantly black women. High levels of unemployment, poverty and gender inequality are key factors driving sex work. The global economic crisis has aggravated the situation for the poor majority through job losses, casualisation and ultimately increased feminization of poverty. Cosatu has already started some debates and campaigns aimed at devising ways of protecting sex workers through collective workers struggles. As such, the sex work discourse and campaign among Cosatu affiliates for decriminalization was tabled at the Federation’s 10th Congress though it was deferred because of contestation and opposition amongst delegates. However, affiliates had the responsibility to go back and make further consultations, sensitization with their structures and open up a discussion at the level of the COSATU Central Executive Committee. Indeed, it is high time that the debate on decriminalization should be concluded and that sex work be recognized as work as Arnott and Crago (2009) argue that: “The criminalisation of sex work has precluded the enforcement and protection of sex workers’ Labour rights. This disregard for sex workers as workers has left many of those employed in brothels in South Africa vulnerable to labor abuses such as withheld wages, arbitrary fines, restrictions on mobility, and confiscation of belongings including medication. Sex workers on the street or working in brothels and other agencies have no recourse if customers refuse to pay them’’1 The decriminalization of sex work should take the course of a rights- based approach which means that sex workers would be able to enjoy their basic human & labour rights and be protected against sexual harassment, violence, rape and unfair working conditions. By so doing, sex workers would be able to access non-discriminatory health care services, be more empowered and operate within the ambit of protective labour and occupational health & safety laws.
- Full Text:
- Date Issued: 2012
Single walled carbon nanotubes functionalized with nickel phthalocyanines
- Khene, Samson, Nyokong, Tebello
- Authors: Khene, Samson , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245843 , vital:51410 , xlink:href="https://doi.org/10.1142/S1088424611004439"
- Description: In this work we report on electrochemical behavior of nickel phthalocyanine derivatives tetrasubstituted peripherally and non-peripherally with hydroxy and used to modify single walled carbon nanotubes. Nickel phthalocyanine complex octasubstituted at the peripheral positions with hydroxy groups was also used to modify single walled carbon nanotubes. Nickel phthalocyanine complex tetrasubstituted with amino groups at peripheral position was covalently and non-covalently linked to single walled carbon nanotubes. All the conjugates of nickel phthalocyanine derivatives with single walled carbon nanotubes were used for the electro oxidation of 4-chlorophenol. The nickel phthalocyanine octabsubstituted with hydroxy groups at the non-peripheral positions gave the best current response and the best resistance against electrode fouling for the oxidation of 4-chlorophenol.
- Full Text:
- Date Issued: 2012
- Authors: Khene, Samson , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245843 , vital:51410 , xlink:href="https://doi.org/10.1142/S1088424611004439"
- Description: In this work we report on electrochemical behavior of nickel phthalocyanine derivatives tetrasubstituted peripherally and non-peripherally with hydroxy and used to modify single walled carbon nanotubes. Nickel phthalocyanine complex octasubstituted at the peripheral positions with hydroxy groups was also used to modify single walled carbon nanotubes. Nickel phthalocyanine complex tetrasubstituted with amino groups at peripheral position was covalently and non-covalently linked to single walled carbon nanotubes. All the conjugates of nickel phthalocyanine derivatives with single walled carbon nanotubes were used for the electro oxidation of 4-chlorophenol. The nickel phthalocyanine octabsubstituted with hydroxy groups at the non-peripheral positions gave the best current response and the best resistance against electrode fouling for the oxidation of 4-chlorophenol.
- Full Text:
- Date Issued: 2012
Spectral, photophysical and photochemical properties of tetra-and octaglycosylated zinc phthalocyanines
- Iqbal, Zafar, Masilela, Nkosiphile, Nyokong, Tebello, Lyubimtsev, Alexey, Hanack, Michael, Ziegler, Thomas
- Authors: Iqbal, Zafar , Masilela, Nkosiphile , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244428 , vital:51256 , xlink:href="https://doi.org/10.1039/c2pp05348a"
- Description: Photophysical and photochemical properties of a series of tetra- and octaglycosylated zinc phthalocyanines (ZnPcs) substituted with glucose and galactose moieties have been reported. Spectral properties of these phthalocyanines are compared in DMSO. Absorption spectra of the non-peripherally tetra-substituted ZnPcs 2 showed a significant red shift in their Q-band maxima as compared to the peripherally substituted analog 1. All the complexes gave high triplet quantum yields ranging from 0.68 to 0.88, whereas triplet lifetimes were in the range of 100–430 µs in argon-saturated solutions. The octagalactosylated ZnPc 3b showed the highest triplet quantum yield and singlet oxygen quantum yield of 0.88 and 0.69, respectively. The fluorescence quantum yields and lifetimes of all the compounds under investigation were within the range of zinc phthalocyanine complexes.
- Full Text:
- Date Issued: 2012
- Authors: Iqbal, Zafar , Masilela, Nkosiphile , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244428 , vital:51256 , xlink:href="https://doi.org/10.1039/c2pp05348a"
- Description: Photophysical and photochemical properties of a series of tetra- and octaglycosylated zinc phthalocyanines (ZnPcs) substituted with glucose and galactose moieties have been reported. Spectral properties of these phthalocyanines are compared in DMSO. Absorption spectra of the non-peripherally tetra-substituted ZnPcs 2 showed a significant red shift in their Q-band maxima as compared to the peripherally substituted analog 1. All the complexes gave high triplet quantum yields ranging from 0.68 to 0.88, whereas triplet lifetimes were in the range of 100–430 µs in argon-saturated solutions. The octagalactosylated ZnPc 3b showed the highest triplet quantum yield and singlet oxygen quantum yield of 0.88 and 0.69, respectively. The fluorescence quantum yields and lifetimes of all the compounds under investigation were within the range of zinc phthalocyanine complexes.
- Full Text:
- Date Issued: 2012
Spectroscopic and physicochemical behavior of magnesium phthalocyanine derivatives mono-substituted with a carboxylic acid group
- Nombona, Nolwazi, Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244450 , vital:51258 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.12.051"
- Description: This work reports on the synthesis of novel unsymmetrically substituted magnesium phthalocyanine complexes containing one carboxyl group. The physicochemical behavior of these complexes were compared with those of their unmetallated and zinc counterparts. The MgPcs showed interesting absorption spectra with [8,15,22-Tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenyl)phthalocyaninato]magnesium (II) showing a large split in the Q band whereas [8,15,22-Tris-(naphtho)-2-(carboxy) phthalocyaninato]magnesium(II) presented only a small splitting. The magnesium phthalocyanine derivatives displayed higher fluorescence quantum yields compared to unmetallated and zinc phthalocyanine counterparts. The latter gave admirable triplet and singlet oxygen quantum yields. These molecules can distinctly be employed in the field of photodynamic therapy in combination with fluorescence imaging.
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244450 , vital:51258 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.12.051"
- Description: This work reports on the synthesis of novel unsymmetrically substituted magnesium phthalocyanine complexes containing one carboxyl group. The physicochemical behavior of these complexes were compared with those of their unmetallated and zinc counterparts. The MgPcs showed interesting absorption spectra with [8,15,22-Tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenyl)phthalocyaninato]magnesium (II) showing a large split in the Q band whereas [8,15,22-Tris-(naphtho)-2-(carboxy) phthalocyaninato]magnesium(II) presented only a small splitting. The magnesium phthalocyanine derivatives displayed higher fluorescence quantum yields compared to unmetallated and zinc phthalocyanine counterparts. The latter gave admirable triplet and singlet oxygen quantum yields. These molecules can distinctly be employed in the field of photodynamic therapy in combination with fluorescence imaging.
- Full Text:
- Date Issued: 2012